Lamp regulating system



Dec. 30, 1941. w E WESTENDQRP 2,268,231

LAMP REGULATING SYSTEM Filed July 13, 1939 I I I lu l AMPS. 0,0.

50 80 I00 12.0 I40 I60 I80 200 LINE VO LTS A.C,.

Inventor: Wi I lem F Westendorp,

His Attorney.

, either the eflicienc in accordance with the discharge current, the

.at one end in a bulbo of oppositely directed Patented Dec. 30, 1941 2,268,231 mmraacumrmc. SYSTEM Schenectady, N. Y., as-

Willem F; Westendorp, signer to 'General Elec tlon of New York trie Company, a corpora- Applicatiorr July 13, 1939, Serial No. 284,271 2 Claims. (or. 176-124) The present invention relates to improved means for operating positivecolumn lamps.

Because of their possession of a negative voltampere characteristic, lamps of the nature specifled are not inherently current limiting. ,For this reason it is common practiceto provide ballast- ,ing means, such as a series resistor or reactor,

in the lamp circuit. This expedient prevents runaway operation, but has an adverse effect on y or the, power factor of the systemas a whole. It isan object of my present invention to provide a novel lamp-regulating means by which both these effects are minimizedl In the attainment of the foregoing object, an

important aspect of the invention consists in the envelope there is provision in the lamp itselfof discharge-controlling means which so regulate the discharge cycle as to produce substantially constant current operation. More specifically, the invention emplo'ys, in a preferred embodiment thereof, a lamp having a single cathode and a plurality of anodes,

each anode being associated with a control electrode or grid. By applying to the various grids ternating control potentials which are variable transfer of such current from one anode to another is regulated in a desired fashion, and the average, current flow is thereby kept within proper limits.

trates diagrammatically the combination of a.

positive column lamp and a circuit for operating the samein accordance with the principles of my invention; 2 comprises a series of graphical 0 representations useful in explaining the invention? and Fig. 3 illustrates the operating characteristics obtainable by the use of the invention.

Referring particularly tojFig. 1 there is shown a discharge lamp comprising a tubular envelope III which is constituted of a light-transmitting materiallsuch as glass. The envelope terminates us portion, designated by the numeral ll, and at theother end in a pair arms, numbered l3 and M respectively. The lamp is of sufficient length so that the tubular portion l0 provides an elongated positive column space. a Within the bulbous portion ll of the envelope, thereis provided a quantityof vaporizable, ioniznected through a condu 30 rent-limiting 21. During inoperative periods of the lamp, the

light emission to occur. If desired, the mercury cathode I5 may be replaced by a solid separately heated cathode, in which case a separate ionizable material, for example, neon gas or a mixture of gases, should be provided as a filling envelope. A fixed ga may also be used advantageouslyeven where a vaporizable cathode is employed.

Above the cathode and preferably outside the band l8 of conductive material which serves to facilitate the initiation of a discharge from the cathode. At the other end of the lamp, within the side arms I3 and Hi there are mounted a pair of anodes 20 and 21 which provide alter-. nately functioning terminals for a discharge proceeding from the cathode I5. For the purposes of the present invention, these anodes are respectively enclosed within perforated grid members designated by the numerals 23 and 24. The utility of the grids 23 and 24 will be described hereinafter.

In the arrangement shown in Fig. 1, the lamp is energized from an alternating current source, indicated at 25. The energizing circuit includes a pair of similar branches 26, 21 which are respectively connected to the terminals of an autotransformer 28. These circuit branches are connected at their terminals tothe anodes 20 and 2| and have a common junction point 29 (a midpoint tap of the transformer 28) which is con ctor 3| to the cathode .15. When the system of line switch 32, the lamp operates as a full wave rectifier, producing a continuous discharge which passes alternately to the anodes 20 and 2|. The discharge current is caused to pass through a reactor 34 whose function will be described more fully hereinafter,

In order to render the lamp initially operative a special starting circuit is provided in connectionwith the starting band l8.v This circuit conmeets the band I8 with one terminal of the autotransformer 28 through a conductor 35, 9. ourresistor 36 and conductors 31 and starting band I8 is shorted to the cathode I5 through a mercury switch 38 whichis movable under the influence of an armature lll associated with the reactor 34.

for the provided a capacity starting is energized by closure Assoon as the switch 32 is closed, a transient surge is produced in the reactor 34 through a circuit which includes conductor 3|, the reactor, switch 38, resistor 36. and conductors 31 and TI. This surge causes motion of the armature 40 and a consequent tilting of the mercury switch 38 to.open its circuit (the switch being thereafter maintained open). At the instant of opening, the relatively high transient voltage existing across the reactor 34 is impressed between the starting band It and the cathode l5 and acts to cause a dischar e to be initiated. This discharge is immediately transferred to the anodes 2|) and 2| and is subsequently maintained by these anodes.

' Inorder to limit current flow through the lamp I0 and at the sometime to assure high efliciency and good regulation of the system as a whole, a. special regulating circuit is provided in connection with the will be brought out in the following, it is desirable that the energization of these grids be made to depend upon the current flow in the discharge circuit. To this end, intermediate terminals 41 and 42 of the auto-transformer 28 are brought out and connected to the primary 44 of a regulating transformer 45. The winding 44 is connected at its midpoint to the cathode supply conductor 3|, so that half of the winding is in series with the circuit branch which, supplies the anode 20, while the other half isin series with the circuit branch which supplies the anode 2|.

grids 23 and. For reasons whichthermore, the current-sustaining eflect '01" the reactor avoids the possibility of. extinguishment ot the discharge at the end of any given voltage cycle. That is to say, the presence of in the system causes current flow to continue even though thevoltage supplied by the autotransformer 28 may be instantaneously reduced to zero.

representation of Fig. 2. ',In this figure the voltage curves V1 and V: respectively representthe voltage applied between the point 29 and the anode 24 and that applied between the point and the anode II. The curves I1 and 1:, on the .other hand, represent the resulting pulses of unidirectional current flow to the two. anodes. The

control voltages applied to the. grids 24 and 23 are indicated by the curves c2 and a: respectively.

It will be understood that the magnitude of the control voltage curves is proportional to that of the current curves and that these curves are displaced in phase due to the action of the condenser 48.

a It is assumed that the lamp initially becomes conductive at the instant to, when the voltage V;

' has reached a predetermined positive value. As

The transformer 45 is provided with a secondary the current I1 tends to increase, the potential I applied to the grid 24' increases in a negative sense as indicated by the curve ea. At a later time, as the current 11 begins to diminish in accordance with the previous decrease of the voltage V1, the voltage e2 also decreases in negative circuit, these quantities being obviously proportional in magnitude.

The operation of the system above described is as follows: After the tube has been started and the current has reached the value set by the grid control, the discharge current flowing through the primary of the transformer develops a voltage across the condenser 48 which lags with respect to the current. With the connections shown, the grid associated with any given anode becomes negative during the period when the other anode is carrying current. Fur-* thermore, the negative polarity of such grid is maintained through the point at which commutation of the discharge to its associated anode tends to occur. The transfer of the current from one anode to the other is, therefore, regulated by the grid voltage and, more fundamentally, in accordance with the variations rent itself.

The fact that the grid circuit is floating (i. e.

of the discharge .cur-

, not connected to any of the other electrodes) simplifies the circuit and improves its operation The grid around the running anode can never be more positive than that anode. Consequently,

if the transformer 45 is connected in the proper way, the grid associated with the inactive anode will be negative when the arc current first tends to shift to that anode and will thus delay the instant of shifting.

It is the function of the reactor 34 to exert a smoothing effect on the discharge currentand thereby to reduce flickering. of the lamp. Furpotential as soon as it becomes positive with re-.

spect to the other grid.

In the event that the average value of current through the lamp tends to increase, as indicated, for example by the curve 11', the negative grid voltage similarly increases to a value c2, and commutation of the discharge is delayed to a time is. As a result, "the average potential supplied by the auto-transformer during the next succeeding conducting 'interval (being made up of a shortened positive component and a lengthened negative component) is reduced and the average current flow is diminished accordingly. Since this regulatoryefiect occurs for'each current cycle, it will be understood thatstability of the system as a whole is assured. 1

The type of regulation obtained with a circuit such as that described above is illustrated in Fig. 3 wherein the curves A and B respectively represent characteristics obtained by varying the line voltage with'two different adjustments of the elements 48 and 49. In these curves, the decrease in current noted as one approaches higher values of operating linevoltage is primarily a result of increased magnetizing current flowing ing characteristic could be obtained by use of a f transformer of greater capacity. v

The point z is assumed to be taken at theapproximate center of the desired operatingrange of the lamp. Under these conditions and especially for the curve A', it will be seen that subthe cathode through a stantially flat regulation of the system may be obtained for an-appreciable range of voltage variation. This is a result which is quite unobtainable when regulation issought simply by the use of series ballasting means. In the latter case, the lamp current tends to increase linearly with the line voltage, as indicated, for example, by the dotted line C of Fig. 3.

The system described represents a marked improvement in efficiency over systems employing resistor control in that the regulation obtained involves no dissipation of power. Furthermore, although some effect on power factor is to be noted as a result of the phase shift of current and line voltage due to the grid control, this effect is materially less than that occurring in cases where a series reactor is used in the alternating current supply line as a ball'asting means or Where a high reactance power transformer is employed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1..In combination, a positive column lamp having a cathode and a pair of anodes, a current supply circuit for said lamp including a pair of similar circuit branches having a common junction point, the said branches being connected at their respective terminals to the said anodes and being connected at their said junction point to series reactor, a source of alternating potential connected in said current supply circuit so as to produce through the lamp a discharge which tends to transfer cyclically from one anode to the other, a pair ofgrids respectively associated with the said anodes and effective to control the initiation of a discharge thereto, and a transformer including a primary winding having similar parts thereof respectively connected in serieswith both of the said circuit branches and a secondary winding terminally connected to the said grids, whereby regulation of the lamp is accomplished by controlling the transfer of the discharge from one anode to the other in automatic response to variations in magnitude of the discharge current.

2. In combination, a positive column lamp having a cathode and a pair of anodes, a current supplycircuit for said lamp including a pair of similar circuit branches having a common junction point, the said branches being connected at their respective terminals to the said anodes and being connected at their said junction point to the cathode, means including a source of alternating potential connected in said current supply circuit to produce through the lamp a discharge which tends to transfer cyclically from one anode to the other, a pair of grids respectively associated with the said anodes, each such grid being effective to control the initiation of a discharge to its associated anode in accordance with the variations of a voltage applied to the grid, and means for applying an alternating voltage to the said grids. for regulating the transfer of the discharge from one anode to the other, the said voltage applying means being excited responsively to current flow in the said current supply circuit, whereby the regulating action of such means varies in direct response to variations in the magnitude of the discharge current and in a manner tending to maintain the discharge current relatively constant.

WILLEM F. WESTENDORP. 

